put (one's) hand in (one's) pocket

To donate money to charity or to those in need of financial assistance. Even though he didn't have much to his name, John was always willing to put his hand in his pocket for people in the community who needed help. I hate it when charity workers on the street try to make you feel guilty for not putting your hand in your pocket.

put your hand in your pocket

spend or provide your own money.

put your ˌhand in/into your ˈpocket

(British English) spend or give money: One of our colleagues is retiring, so I expect they’ll want us to put our hands into our pockets for a present. ♢ He’s one of the meanest men I know. He never puts his hand in his pocket for anything.